I have a similar stove, the jotul f500, and had a similar problem. I discovered that the elbow had failed and split apart..causing insufficient draft. I couldn't get the wood to burn very well and tons of smoke was coming into the house every time I opened the door. After replacing the elbow (for about 15 bucks) I'm back in action. No smoke and wood burning much better.
I also wouldn't use the ash door for draft..I was told that using the bottom door causes a "flame thrower" effect and can heat your stove up too quickly. If I need more draft for some reason I open the side door. Not sure if you have one on that model though.
Hope your fix was as easy as mine...happy burning!
